In the manufacture of crankshafts it is necessary to grind the crank pins of the crankshaft to size on a grinding machine. To ensure that the grinding operation is terminated as soon as a desired dimension is reached, the crank pin must be continuously checked during the machining operation, in particular with regard to its diameter and roundness, within the scope of an in-process measuring operation. EP-A-0859689 discloses such a measuring device.
A measuring device is known from EP-A-1370391 which is used for in-process measurement of crank pins during a grinding operation on a grinding machine. The known measuring device has a measuring head which is connected via a rod assembly to a base body of the measuring device so as to be pivotable about a first pivot axis. The known measuring device also has a means for swiveling the measuring head in and out of a measuring position. For carrying out an in-process measurement on a crank pin, the measuring head is swiveled by the means provided for this purpose into a measuring position in which the measuring head, for example by means of a measuring prism, comes to rest on the crank pin to be measured. The crank pin undergoes an orbital rotation about the rotational axis of the crankshaft during the grinding operation. In this manner, the grinding wheel remains in contact with the crank pin, and for this purpose is movably supported radially with respect to the rotational axis of the crankshaft. To ensure that measurements may be carried out on the crank pin during the entire grinding operation, the measuring head follows the movements of the crank pin. For this purpose, the base body of the measuring device is connected to a base body of the grinding machine, so that during the grinding operation the measuring device is moved synchronously with the grinding wheel of the grinding machine in the radial direction of the crankshaft. Similar measuring devices are also known from DE 2009/052254 A1 and DE 2010 013 069 A1.
A measuring device of the type in question for in-process measurement of test pieces during a machining operation on a machine tool is known from EP 1 263 547 B1, having a base body, and a measuring head which is movable between a neutral position and a measuring position and which is connected to the base body via a rod assembly which is designed and set up in such a way that the measuring head in the measuring position follows orbital rotations of the test piece about a rotational axis, the measuring head having a measuring sensor which is deflectable along a linear axis for recording measured values during a measuring operation. The measuring device known from the cited publication also has a control apparatus for controlling the measuring operation, the measuring device being provided for measuring the diameter and roundness of crank pins of a crankshaft during a machining operation on a grinding machine.